Manually releasable grounding electrical plug



April 13, 1965 M. MORSE 3,178,667

MANUALLY RELEASABLE enounnme ELECTRICAL PLUG Filed July 13, 1962 2 Sheets-Sheet 1 I *I F92 3,178,667 'MANUALLY RELEASABLE GROUNDING ELECTRICAL PLUG Filed July 13. 1962 M. MORSE April 13, 1965 2 Sheets-Sheet 2 United States Patent M 3,178,667 MANUALLY RELEASABLE GROUNDING ELECTRICAL PLUG Milton Morse, 41 Honeck St., Englewood, N.Y. Filed July 13, 1962, Ser. No. 209,579 Claims. (Cl. 339-14) This invention relates generally to the field of grounding electrical plugs of a type employing, in addition to the normally-present power prongs, a grounding prong adapted to engage a separate portion of an electric outlet receptacle. Devices of this type are generally known in the art, and the invention lies in specific constructional details, permitting greater convenience in use together with a high degree of safety, and in a means for manufacturing the improved structure at reasonable cost.

While it is known in the art to provide a grounding blade which is pivotally mounted upon a plug body in such manner as to be deflected upon the engagement of the plug with a non-grounded receptacle, so that the blade may establish a ground with respect to the cover plate of the receptacle, such devices have not been entirely satisfactory and have failed to obtain approval of certifying agencies. Where the pivotally mounted grounding prong or blade is only resiliently urged to a position in which the same lies parallel to the power prongs, accidental contact of the fingers of the user, or other object, may readily deflect the same from a parallel relation, wherein the grounding member will not enter the grounding opening of a grounded receptacle where such receptacle is not visible to the user. Further, where the grounding blade is only resiliently maintained in operative position, it can be accidentally deflected to a degree wherein the power prongs may engage the receptacle without the grounding prong first establishing an electrical ground, either with the grounding opening of the receptacle or the face plate, thereby subjecting the user to the possibility of a severe shock.

It is therefore among the principal objects of the present invention to provide an improved grounding plug of the class described in which the above-mentioned disadvantages have been substantially eliminated.

Another object of the invention lies in the provision of an improved grounding-type plug in which the grounding blade thereof may be held rigidly in the grounding position by manually-operated mechanical latching means.

Another object of the invention lies in the provision of an improved grounding-type plug of the class described in which the latching means operates automatically to lock the blade in grounding position upon being returned from a displaced position thereto by resilient means.

Another object of the invention lies in the provision of an improved self-restoring grounding blade plug construction including a finger-operated mechanical latching means in which the manual release of the means serves to deflect the grounding blade through a small arc only, thereby assuring further deflection upon contact with the face plate of a receptacle, and preventing entry of power prongs into the receptacle prior to the establishment of a ground by the grounding blade.

Still another object of the invention lies in the provision of an improved grounding plug having a latched grounding blade, in which the latching means is electrically insulated from the grounding blade as an additional safety feature.

Yet another object of the invention lies in the provision of an improved grounding-type plug in which the grounding blade is provided with means for giving a clear indication to the user if the grounding blade has not entered a grounding hole in a receptacle.

A further object of the invention lies in the provision 3,178,667 Patented Apr. 13, 1965 of an improved grounding-type plug particularly adapted for use in conjunction with hand-held electrical tools and appliances, wherein the possibility of shock to the user is greater than in the case of other appliances.

A further object of the invention lies in the provision of improved machine tool means for manufacturing a grounding electrical plug possessed of the above advantages.

A feature of the invention lies in the fact that a single resilient component may be employed to provide both grounding blade return and locking function.

Another feature of the invention lies in the fact that the disclosed embodiments may be manufactured at least partially as tool machine operations, thereby maintaining the cost of production at reasonable levels, comparable with that of existing prior art devices.

These objects and features, as well as other incidental ends and advantages, will more fully appear in the progress of the following disclosure, and be pointed out in the appended claims.

In the drawings, to which reference will be made in the specification, similar reference characters have been employed to designate corresponding parts throughout the several views.

FIGURE 1 is a side elevational view of a first embodiment of the invention.

FIGURE 2 is a central longitudinal sectional view thereof, partly in elevation.

FIGURE 3 is a side elevational view thereof, showing the'side opposite that seen in FIGURE 1.

FIGURE 4 is a bottom plan view thereof.

FIGURE 5 is a view in elevation of a grounding blade element which comprises a part of the first embodiment, prior to complete forming thereof.

FIGURE 6 is a similar view in elevation of the grounding blade element in fully formed condition.

FIGURE 7 is an elevational view of a modification of the grounding blade element during one step in fabrication.

FIGURE 8 is a sectional view as seen from the plane 88 in FIGURE 7.

FIGURE 9 is an elevational view corresponding to FIGURE 7 but showing an ensuing step in fabrication.

FIGURE 10 is a sectional view as seen from the plane 1il10 in FIGURE 9.

FIGURE 11 is an elevational view showing the modification of FIGURE 7 in finished condition and form.

FIGURE 12 is a view in elevation showing a resilient element comprising a part of the first embodiment.

FIGURE 13 is a longitudinal central sectional view as seen from the plane 13-13 in FIGURE 12.

FIGURE 14 is a view in elevation as might be seen from the right-hand portion of FIGURE 13.

FIGURE 15 is a view in elevation of a cover element comprising a part of the first embodiment.

FIGURE 16 is a longitudinal central sectional view of the cover element as seen from the plane 1616 in FIG- URE 15.

In accordance with the first embodiment of the invention, the device, generally indicated by reference character 10, comprises broadly: a plug body element 11; first and second power prongs 12 and 13, respectively; a grounding blade element 14; a resilient cam element 15; and an insulative cover or button element 16.

The plug body element 11 is preferably of molded rubber construction, although if desired the same may be also formed from phenolic resins and similar substances. It is bounded by an upper surface 20, side surfaces 21, 22, 23, 24, 25 and 26. Extending inwardly into the body element from the surface 26 is a recess 27 bounded by first, second and third planar surfaces 28, 29 and 30, respectively, and a cylindrical surface 31 disposed coam'ally with respect to a transversely disposed bore 32 which extends completely through the body element 11. The bore 32 is lined with a brass or other conductive bushing 33, and is connected to a grounding conductor (not shown) in well-known manner.

Disposed opposite the recess 27 is an elongated recess 34 bounded by a bottom surface 35, side surfaces 36 and 37, and end surfaces 38 and 39. Disposed at the upper periphery of the recess 34 are lip members 40, 41 and 42, which serve to retain the cover element 16 in position, as will more fully appear.

The first and second power prongs 13 and 14, respectively, are of conventional construction, and may be embedded within the plug body 11 at the time the latter is molded. The outer ends 45 and 46 project outwardly a distance less than the distance the grounding blade element 14 projects when in aligned position with respect to the principal axes of the power prongs 12 and 13, so as to assure that a ground will be established before the outer ends 45 and 46 contact the corresponding contacts within the openings in an electric receptacle.

With reference to FIGURES and 6, the grounding blade element 14 is formed from a readily machined electrical conductive material such as brass, and includes a receptacle-engaging member 48, a curved member 49, a transversely disposed cylindrical member 50, an axially aligned member of rectangular cross section 51, a spiral member 52, a second member of rectangular cross section 53, and -a button or terminal 54.

The curved member 49 is formed in such a manner as to include a small shelf 55 which serves the function of positioning the transversely disposed cylindrical member 50 within the bushing 33.

The member 51 is, as has been mentioned, axially aligned with respect to the axis of the member 50, and is bounded by first and second planar surfaces 56 and 57, tapered surfaces 58 and 59, and arcuate surfaces 60 and 61 which are continuations of the outer surface of the member 50.

The spiral member 52 is bounded by two arcuate surfaces 62 and 63, and spiral surfaces 64 and 65. As best seen from a consideration of FIGURE 5, it will be observed that the thickness of the spiral member 52 is substantially less than that of the member 51 for reasons which will more clearly appear. The member 53 includes first and second planar surfaces 66 and 67, and may be of the same thickness as the member 52. The button or terminal 54 is bounded by a radial surface 69, a cylindrical surface 70, and a conical surface 71.

With reference to FIGURES 12 to 14, inclusive, the resilient cam element 15 is preferably formed as a stamping, from brass or other resilient material, and includes a base member 74, a connecting bend portion 75, and a resiliently flexing member 76. The base member 74 is bounded by a curvilinear edge 77, outer side edges 78 and 79, from which depend resilient tabs 80 and 81, and inner side edges 82 and 83. Extending through the plane of the base member 74 is a circular opening 84 with which a slotted opening 85 communicates.

The resilient flexing member 76 is bounded by side edges 87 and 88, as well as a curvilinear edge 89. It is provided with a circular opening 90, the dimensions of which are similar to those of the opening 84, being of sufiiciently large diameter to permit passage of the button or terminal 54.

With reference to FIGURES 15 and 16, the cover or button element 16 is preferably formed from synthetic resinous material so as to possess the quality of electrical insulation. It includes an outer wall 94, side walls 95 and 96, having first and second tabs 97 and 98 thereon, and a curved end Wall 99 having third and fourth tabs 100 and 101 thereon. At the narrower end of the side walls 95 and 96 are notches 102 and 103 formed by the tabs 97 and 98, respectively, the notches 102 and 103 being adapted to engage the ends of the tabs 80 and 81 during assembly. The undersurface 104 of the outer wall 94 is provided with a circular recess 105 adapted to engage the conical surface 71 of the button or terminal 54.

During assembly, the grounding blade element 14 is inserted into the bushing 33 so that the terminal 54 pro jects outwardly into the recess 34. The cam element 15 is then positioned within the recess 34 in such manner that the slotted opening engages the spiral member 52, the terminal 54 projecting through both the opening 84 and the opening 90. The cam element 15 is maintained in position by slipping a small split washer 107 to engage the radial surface 69, and prevent passage again through the circular Openings. Following this, the cover element 16 is positioned in such manner that the tabs and 101 are disposed beneath the lip members 40 and 41, and the tabs 97 and 98 beneath the lip member 42, respectively.

In engaging the device 10 within a receptacle, where a grounding prong opening is present, the resilient force of the cam member 15 will retain the grounding blade element 14 in locked condition wherein the receptacle-engaging member 48 is axially aligned parallel to the power prongs 12 and 13. When in this locked condition, it cannot be manually moved out of aligned condition without depressing the cover element 16. Where the outlet receptacle does not have a grounding prong opening, the user will not be able to insert the plug without first unlocking the grounding blade element 14 by pressing inwardly on the cover element 16. Upon the exertion of pressure, the imparted motion is transmitted through the slotted opening 85 to the spiral member 52, to result in deflecting the grounding blade element 14 through a small arc, preferably under thirty degrees. The blade will remain in deflected condition for so long as pressure is maintained upon the cover element 16. During this slight deflection, owing to the fact that the grounding blade element 14 is of greater length than the power prongs 12 and 13, the grounding blade element 14 will not be deflected a distance sufiicient to permit the power prongs 12 and 13 to contact the outlet prior to the grounding blade element making contact with the face plate of the receptacle to establish a ground, thereby preventing all possibility of a shock being transmitted to the user. This degree of deflection is sufiicient to permit continued further deflection upon striking of the face plate, to a degree sufiicient to permit the power prongs to be fully seated within the receptacle.

Upon removal of the plug from the receptacle, the resilient cam element 15 returns to its unstressed condition, and in doing so transmits motion to the grounding blade element 14 to return it to aligned condition with respect to the power prongs. Following the reaching of an aligned condition, the slotted opening 85 engages the member 51 to lock the grounding blade element 14 in aligned condition until pressure again is applied to the cover element 16.

In the modification of the grounding blade element shown in FIGS. 1721, to avoid repetition, corresponding parts are given the same reference character with the suflix a. Element 14a differs in that the portion which forms the spiral member 5211 during the process of fabrication is first reduced in diameter (FIGS. 17 and 18); then the flats are milled (FIGS. 19 and 20); and are finally twisted. The reduced distance between the edges 52c and 52d, requires less stretching of said edges during twisting, resulting in a smoother superior spiral member.

I wish it to be understood that I do not consider the invention limited to the precise details of structure shown and set forth in this specification, for obvious modifications will occur to those skilled in the art to which the invention pertains.

I claim:

1. In a grounding electrical plug having a plug body, at least one power prong extending outwardly of said body, and a grounding prong pivotally mounted upon said body and normally extending parallel to said power prong, the improvement comprising: said grounding prong having a transversely disposed portion thereof extending through said plug body having an axis perpendicular to the axis of said power prong about which pivotal movement may take place, resiliently mounted means movable in a direction generally parallel to said transversely disposed portion, cam and cam follower means interconnecting said resiliently urged means and said transversely disposed portions to transmit rectilinear motion impressed upon said resilient means to rotational movement of said transversely disposed portion wherein said grounding prong is moved to a non-parallel relation with respect to said power prong.

2. In a grounding electrical plug having a plug body, at least one power prong extending outwardly of said body, and a grounding prong pivotally mounted upon said body and normally extending parallel to said power prong, the improvement comprising: said grounding prong having a transversely disposed portion thereof extending through said plug body having an axis perpendicular to the axis of said power prong about which pivotal movement may take place, said portion having cam follower means thereon, cam means resiliently mounted upon said plug body and movable in a direction generally parallel to the axis of said transversely disposed portion and contacting said cam follower portion thereof to impart movement thereto tending to move said grounding prong to a non-parallel relation with respect to said power prong.

3. In a grounding electrical plug having a plug body, at least one power prong extending outwardly of said body, and a grounding prong pivotally mounted upon said :body and normally extending parallel to said power prong, the improvement comprising: said grounding prong having a transversely disposed portion thereof extending through said plug body having an axis perpendicular to the axis of said power prong about which pivotal movement may take place, said portion having cam follower means thereon, cam means resiliently mounted upon said plug body and movable in a direction generally parallel to the axis of said transversely disposed portion and contacting said cam follower portion thereof to impart movement thereto tending to move said grounding prong to a nonparallel relation with respect to said power prong; said cam means when moving in an opposite direction under the influence of said resilient means tending to urge said grounding prong to a parallel position with respect to said power prong.

4. In a grounding electrical plug having a plug body, at least one power prong extending outwardly of said body, and a grounding prong pivotally mounted upon said body and normally extending parallel to said power prong, the improvement comprising: said grounding pron-g having a transversely disposed portion thereof extending through said plug body having an axis perpendicular to the axis of said power prong about which pivotal movement may take place, said portion having camfollower means thereon, cam means resiliently mounted upon said plug body and movable in a direction generally parallel to the axis of said trans-versely disposed portion and contacting said cam follower portion thereof to impart movement thereto tending to move said grounding prong to a non-parallel relation with respect to said power prong; said cam means when moving in an opposite direct-ion under the influence of said resilient means tending to urge said grounding prong to a parallel position with respect to said power prong, and locking means for maintaining said grounding prong in parallel relation with respect to said power prong.

5. In a grounding electrical plug having a plug body, at least one power prong extending outwardly of said body, and a grounding prong pivotally mounted upon said body and normally extending parallel to said power prong, the improvement comprising: said grounding prong having a transversely disposed portion thereof extending through said plug body having an axis perpendicular to the axis of said power prong about which pivotal movement may take place, said portion having cam follower means thereon, cam means resiliently mounted upon said plug body and movable in a direction generally parallel to the axis of said transversely disposed portion and contacting said cam follower portion thereof to impart movement thereto tending to move said grounding prong to a non-parallel relation With respect to said power prong; said cam means when moving in an opposite direction under the influence of said resilient means tending to urge said grounding prong .to a parallel position with respect to said power prong, and locking means for maintaining said grounding prong in parallel relation with respect to said power prong, said locking means being actuated by said resilient means.

References Cited in the file of this patent UNITED STATES PATENTS 1,856,724 Phelps May 3, 1932 1,924,962 Rosenbaum Aug. 29, 1933 2,217,496 Riley Oct. 8, 1940 2,323,736 Tousley July 6, 1943 2,876,426 Morse Mar. 3, 1959 2,922,134 Elfenbein Jan. 19, 1960 FOREIGN PATENTS 1,194,663 France May 11, 1959 

1. IN A GROUNDING ELECTRICAL PLUG HAVING A PLUG BODY, AT LEAST ONE POWER PRONG EXTENDING OUTWARDLY OF SAID BODY, AND A GROUNDING PRONG PIVOTALLY MOUNTED UPON SAID BODY AND NORMALLY EXTENDING PARALLEL TO SAID POWER PRONG, THE IMPROVEMENT COMPRISING: SAID GROUNDING PRONG HAVING A TRANSVERSELY DISPOSED PORTION THEREOF EXTENDING THROUGH SAID PLUG BODY HAVING AN AXIS PERPENDICULAR TO THE AXIS OF SAID POWAER PRONG ABOUT WHICH PIVOTAL MOVEMENT MAY TAKE PLACE, RESILIENTLY MOUNTED MEANS MOVABLE IN A DIRECTION GENERALLY PARALLEL TO SAID TRANSVERSELY DISPOSED PORTION, CAM AND CAM FOLLOWER MEANS INTERCONNECTING SAID RESILIENTLY URGED MEANS AND SAID TRANSVERSELY DISPOSED PORTIONS TO TRANSMIT RECTILINEAR MOTION IMPRESSED UPON SAID RESILIENT MEANS TO ROTATIONAL MOVEMENT OF SAID TRANSVERSELY DISPOSED PORTION WHEREIN SAID GROUNDING PRONG IS MOVED TO A NON-PARALLEL RELATION WITH RESPECT TO SAID POWER PRONG. 